f2fs: show checkpoint version at mount time

If we mounted f2fs successfully, let's show current checkpoint version.
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/super.c

@@ -2102,6 +2102,8 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 			sbi->valid_super_block ? 1 : 2, err);
 	}
 
+	f2fs_msg(sbi->sb, KERN_NOTICE, "Mounted with checkpoint version = %llx",
+				cur_cp_version(F2FS_CKPT(sbi)));
 	f2fs_update_time(sbi, CP_TIME);
 	f2fs_update_time(sbi, REQ_TIME);
 	return 0;